The manufacture of fiber glass filaments and particularly textile fiber glass filaments is a high volume manufacturing process involving high temperatures. Typically, the process starts with the mixing of batch ingredients in precise proportions which is then melted in a high temperature furnace. While in the molten state the molten vitreous material is supplied to the bushing. The viscous glass is then drawn from the bushing in a continuous filament form by high speed precision winders through a plurality of filament orifices provided in the bottom wall of the bushing. The filaments are attenuated, cooled and gathered together to form strands.
Any process downtime is costly in terms of equipment replacement and repair and lost product output. Developments are continually being made to the equipment that performs the various fiber glass filament/strand forming functions to improve their overall performance and useful life.
The bushing, which plays a very important role in the overall manufacturing process has been the subject of considerable development efforts.
Examples of such development efforts can be found in U.S. Pat. Nos. 3,511,916; 3,514,841; 3,74,581 and 3,615,314 as well as in a book by K. L. Lowenstein, B.Sc., Ph.D., F.S.G.T. entitled "The Manufacturing Technology of Continuous Glass Fibres"; the first edition published by Elsevier Scientific Publishing Company of Amsterdam, The Netherlands, London, England and New York, N.Y., dated 1973. The second edition of this book was published in 1983 by the same publisher.
While there have been many efforts to improve the performance and useful life of the bushing, none of these efforts have satisfactorily solved the problem of bushing corner flange cracking. When such bushing corner flange cracking occurs, the molten glass may leak from the bushing thus requiring premature and costly bushing removal and replacement.